70.His studies of ice-polished rocks in his Alpine homeland, far outside the range of present-day glaciers, led Louis Agassiz in 1873 to propose the concept of an age in which great ice sheets had existed in now currently temperate areas.
为什么不选D。when great ice sheets had existed in current temperate areas.
这个ice sheets不是在LA这个人提出之前就存在过吗?为什么不用过去完成时?而且有明显过去的提示 led ,,, in 1873之类的,
求指点,谢谢!作者: jenningsyao 时间: 2011-9-24 06:30
我的理解是an age when/in which做时间,应该用一般过去时。作者: triangel8866 时间: 2011-9-25 21:31